Apex domains cannot have CNAME records.
Question and response
Question
dig mailecloud.com. NS
Answer
mailecloud.com. 4 NS pns34.cloudns.net.
mailecloud.com. 4 NS pns33.cloudns.net.
mailecloud.com. 4 NS pns31.cloudns.net.
mailecloud.com. 4 NS pns32.cloudns.net.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0